|Let's have the modem make and model number too, as your general symptoms point to a problem in that area.|
Did you do a full reset of the modem, rather than just powering it off then on again?
Can you see your network name and others when upstairs?
Is the modem located upstairs or downstairs?
"reformatted my laptop twice"
Wow, that sounds like overkill.
Always pop back and let us know the outcome - thanks